Potentiometers



Sept. 16, 1958 G. H. ELLIOTT POTENTIOMETERS Filed April 4. 1956 INVENTOR. George H. Ell/0f? BY I @Ma HTTOR/VEVS l 2,852,644 Fatented Sept. 16, 1958 POTENTIOMETERS GeorgeH. Elliott, Van Nuys, Calif., vassignor, by mesne assignments, to Don M. Hallerberg, Los Angeles, Calif.

Application April 4, 1956, Serial No. 576,010

2 Claims. (Cl. 201-48) This invention relates to potentiometers or similar variable resistance devices and has for its primary object to provide an improved contact mechanism for such a device.

An important object of the invention is also to provide a device in which the parts are so arranged that a plurality of resistance units may be ganged for operation from a common shaft.

Other objects and advantages will become apparent from the following detailed description of a preferred embodiment of the invention, reference being had to the accompanying drawings, in which- Fig. 1 is a perspective view of a potentiometer embodying the present invention;

Fig. 2 is an enlarged central vertical sectional view of the potentiometer with a dotted-line disclosure of a second unit ganged for common operation with the first;

Figs. 3 and 4 are sections on lines 33 and 4--4 of Fig. 2; and

Fig. 5 is a fragmentary section on line 55 of Fig. 3.

Referring to the drawings, the potentiometer of the present invention comprises a housing having a front portion 11 axially separated from a rear portion 12. The front housing portion carries a circular resistance element 14 in a suitably formed axially extending recess. The front housing portion is also provided with a front bearing plate 16 in which an anti-friction bearing may be mounted if desired, the anti-friction bearing being designated 18.

The rear housing portion 12 interfits axially and circumferentially with the front housing portion 11 in any suitable manner and is provided with a circular contact element or slip ring 20 preferably of a diameter similar to the diameter of the circular resistance element 14 so that the two are axially separated but brought almost face to face in substantially parallel planes when the front and rear housing portions 11 and 12 are in assembled position. It will be noted that the area of the rear housing portion 12 within the contact ring 20 is unobstructed and unoccupied with any terminals or other devices.

The resistance element 14 may be of any suitable form but is preferably composed of an insulated base wire 24 around which is a fine resistance wire is wound in a known manner, the resistance wire being brought off at each end to contacts 26 and 28 which are anchored in the front housing portion 11. The wire may be connected to the contacts in any suitable manner as by staking it in place with small pins 30 and 32 or, if desired, by soldering it in place. The resistance wire is, for example, disposed over 358 of the circumference of a circle so that there is a small space between the ends of the wire as best shown in Fig. 3.

The contact mechanism hereinafter described is operated by a centrally disposed shaft 35 which is received in the anti-friction bearing 18 and which extends through the bearing plate and through a suitable opening in the front housing portion 11. The shaft is made integral with an insulating portion 36 so that it can receive the slider or contact mechanism and not enter into the electrical functions of the mechanism. Since the shaft is mounted in an anti-friction bearing the resistance to turning is made very low and in practice may amount to a fraction, of a gram-inch of torque required to turn the shaft.

The present invention is primarily concerned with the contact mechanism or slider of the potentiometer and these elements are best shown in Figs. 2, 3 and 5. The contact mechanism comprises a spring finger 40 depending from the actuating shaft of the potentiometer and fixed thereto in any suitable manner as by staking. The contact finger 40 rides against the periphery of the resistance element 14 and is further provided with circumferentially extending and diverging spring fingers 42 and 44 as shown in Figs. 3 and 5 which fingers ride against the periphery of the circumferential contact or slip ring 20. The normal position of the spring fingers is such that they are compressed when the front and rear housing portions 11 and 12 are assembled so that the fingers serve to keep a constant contact force against the finger 40 which rides against the resistance element. contact assembly being constantly under spring pressure assures that the contact potential of the potentiometer will be very low and the electrically conducting surfaces kept clean by the sliding action of the contact assembly.

Electrical connection to the slip ring or stationary contact 20 is made by staking a pin 46 radially through the wall of the rear housing portion 12 and into contact with the ring 20. The pin 46 serves the dual function of retaining the ring in the housing and providing an electrical connection thereto.

The dottedline portion of Fig. 2 shows the manner in which the units may be ganged together. It is only necessary to drill an opening in the rear wall of the rear housing portion 12 of a diameter suitable for the reception of the shaft 35a of a second potentiometer and to make this shaft long enough to be frictionally received in a central opening 36a in the insulating portion 36 of the front potentiometer of the series. It will thus be seen that turning the shaft of the front potentiometer of the ganged series will result in turning the shaft of the second of the series and that the two potentiometers will operate in complete synchronism. Additional units maybe similarly ganged to Whatever extent is desired.

The front and rear housing portions of the potentiometer may be held together in any suitable manner either by dowel pins or by a snap ring 50. The manner of locating the housing portions relative to each other and retaining them in fixed position is not a part of the present invention. If the snap ring 59 is used it may take the form of a wire inserted into a suitable groove after the front and rear housing portions have been brought into assembled relationship and the ends of the wire extended out through a small opening 52 (Fig. 3) in the periphery of the rear housing portion.

While the invention has been disclosed in conjunction with a specific form and disposition of the parts, it should be expressly understood that numerous modifications and changes may be made without departing from the scope of the appended claims.

What I claim is:

1. In a potentiometer having a circular resistance element, a circular contact ring facing said resistance ele ment in a plane substantially parallel to the plane of the resistance element, a contact assembly comprising a radial spring finger disposed against said resistance element and circumferentially extending diverging fingers disposed against said contact ring, a central operating shaft operatively connected to said radial spring finger, and means to establish electrical connections to said resistance element and to said contact ring.

The

2. In a potentiometer, front and rear axially separable housing portions having facing recesses formed therein, a circular resistance element disposed in the recess in said front housing portion, a circular contact ring disposed in the recess insaid rear housing portion, the area Within said contact ring being unoccupied, a contact assembly comprising a radial spring finger disposed against said resistance element and circumferentially extending diverging fingers disposed against said contact ring, a central operating shaft journaled in said front housing portion and operatively connected to said radial spring finger, and means to establish electrical connections to said resistance element and to said contact ring, said means extending radially through said front and rear housing portions respectively.

References Cited in the file of this patent UNITED STATES PATENTS 2,033,591 Schellenger Mar. 10, 1936 2,255,132 Stoekle Sept. 9, 1941 2,572,651 Mucher Oct. 23, 1951 2,657,295 Barclay Oct. 27, 1953 

